1// Ceres Solver - A fast non-linear least squares minimizer
2// Copyright 2010, 2011, 2012 Google Inc. All rights reserved.
3// http://code.google.com/p/ceres-solver/
4//
5// Redistribution and use in source and binary forms, with or without
6// modification, are permitted provided that the following conditions are met:
7//
8// * Redistributions of source code must retain the above copyright notice,
9//   this list of conditions and the following disclaimer.
10// * Redistributions in binary form must reproduce the above copyright notice,
11//   this list of conditions and the following disclaimer in the documentation
12//   and/or other materials provided with the distribution.
13// * Neither the name of Google Inc. nor the names of its contributors may be
14//   used to endorse or promote products derived from this software without
15//   specific prior written permission.
16//
17// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
18// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
21// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27// POSSIBILITY OF SUCH DAMAGE.
28//
29// Author: sameeragarwal@google.com (Sameer Agarwal)
30//         keir@google.com (Keir Mierle)
31//
32// Purpose : Class and struct definitions for parameter and residual blocks.
33
34#ifndef CERES_INTERNAL_RESIDUAL_BLOCK_H_
35#define CERES_INTERNAL_RESIDUAL_BLOCK_H_
36
37#include <string>
38#include <vector>
39
40#include "ceres/cost_function.h"
41#include "ceres/internal/port.h"
42#include "ceres/internal/scoped_ptr.h"
43#include "ceres/stringprintf.h"
44#include "ceres/types.h"
45
46namespace ceres {
47
48class LossFunction;
49
50namespace internal {
51
52class ParameterBlock;
53
54// A term in the least squares problem. The mathematical form of each term in
55// the overall least-squares cost function is:
56//
57//    1
58//   --- loss_function( || cost_function(block1, block2, ...) ||^2  ),
59//    2
60//
61// Storing the cost function and the loss function separately permits optimizing
62// the problem with standard non-linear least techniques, without requiring a
63// more general non-linear solver.
64//
65// The residual block stores pointers to but does not own the cost functions,
66// loss functions, and parameter blocks.
67class ResidualBlock {
68 public:
69  // Construct the residual block with the given cost/loss functions. Loss may
70  // be null. The index is the index of the residual block in the Program's
71  // residual_blocks array.
72  ResidualBlock(const CostFunction* cost_function,
73                const LossFunction* loss_function,
74                const vector<ParameterBlock*>& parameter_blocks,
75                int index);
76
77  // Evaluates the residual term, storing the scalar cost in *cost, the residual
78  // components in *residuals, and the jacobians between the parameters and
79  // residuals in jacobians[i], in row-major order. If residuals is NULL, the
80  // residuals are not computed. If jacobians is NULL, no jacobians are
81  // computed. If jacobians[i] is NULL, then the jacobian for that parameter is
82  // not computed.
83  //
84  // Evaluate needs scratch space which must be supplied by the caller via
85  // scratch. The array should have at least NumScratchDoublesForEvaluate()
86  // space available.
87  //
88  // The return value indicates the success or failure. If the function returns
89  // false, the caller should expect the the output memory locations to have
90  // been modified.
91  //
92  // The returned cost and jacobians have had robustification and local
93  // parameterizations applied already; for example, the jacobian for a
94  // 4-dimensional quaternion parameter using the "QuaternionParameterization"
95  // is num_residuals by 3 instead of num_residuals by 4.
96  //
97  // apply_loss_function as the name implies allows the user to switch
98  // the application of the loss function on and off.
99  bool Evaluate(bool apply_loss_function,
100                double* cost,
101                double* residuals,
102                double** jacobians,
103                double* scratch) const;
104
105
106  const CostFunction* cost_function() const { return cost_function_; }
107  const LossFunction* loss_function() const { return loss_function_; }
108
109  // Access the parameter blocks for this residual. The array has size
110  // NumParameterBlocks().
111  ParameterBlock* const* parameter_blocks() const {
112    return parameter_blocks_.get();
113  }
114
115  // Number of variable blocks that this residual term depends on.
116  int NumParameterBlocks() const {
117    return cost_function_->parameter_block_sizes().size();
118  }
119
120  // The size of the residual vector returned by this residual function.
121  int NumResiduals() const { return cost_function_->num_residuals(); }
122
123  // The minimum amount of scratch space needed to pass to Evaluate().
124  int NumScratchDoublesForEvaluate() const;
125
126  // This residual block's index in an array.
127  int index() const { return index_; }
128  void set_index(int index) { index_ = index; }
129
130  string ToString() {
131    return StringPrintf("{residual block; index=%d}", index_);
132  }
133
134 private:
135  const CostFunction* cost_function_;
136  const LossFunction* loss_function_;
137  scoped_array<ParameterBlock*> parameter_blocks_;
138
139  // The index of the residual, typically in a Program. This is only to permit
140  // switching from a ResidualBlock* to an index in the Program's array, needed
141  // to do efficient removals.
142  int32 index_;
143};
144
145}  // namespace internal
146}  // namespace ceres
147
148#endif  // CERES_INTERNAL_RESIDUAL_BLOCK_H_
149